Tag: angularjs

This had been bothering me for a while until I stumbled upon an answer that led me to a solution.

With ng-file-upload (https://github.com/danialfarid/ng-file-upload) for AngularJS, you have the capability to resize images using the ngf-resize directive. It’s very handy since you can put some of the CPU processing burden resizing giant images to smaller sizes on the user, rather than to put it on your own server (if you resize the images after the files are uploaded).

HOWEVER, the problem with ngf-resize is when resizing starts, and especially if the user selects multiple images at once, the user’s browser hangs while the images resize. The bigger the image, the longer it takes. This is irritating, and also confusing, causing the user to wonder what is going on. For the longest time I was trying to figure out how to give the user a message before the resizing actually starts.

I eventually stumbled upon the ngf-before-model-change directive part of ng-file-upload. This allows you to define a function that is called before the model changes (and the images start resizing). This is a perfect place to put up a message to the user that their images are about to be resized, and for them to sit tight for the next few seconds.

Then the ngf-select directive can be used to define a function which is called AFTER the resizing is complete, and this is where you can remove the message to the user.

Full example follows like this. In your JavaScript side of things (in your AngularJS controller) you would do:

And that’s it! beforeResizingImages() and afterResizingImages() will be called in the correct order, putting the message up before resizing images (and before the browser hangs for a few seconds for the CPU intensive process), and taking it off after resizing. Note that I use angular-block-ui (https://github.com/McNull/angular-block-ui) to block the UI and put the message up, and of course angular-translate to translate the text for the block message.

So I found many articles on using AngularJS directives, which go into great detail for very complex directives. I couldn’t find any on just a relatively simple directive, so I thought I’d write about it.

First of all, an AngularJS directive defines a reusable HTML tag that you can use in your HTML files. It’s very useful if you want to create some complicated custom tags, or even just simple ones, that you can reuse everywhere.

In my case, I just wanted to give my users a message for them to add the system email to their spam filter allow list, so no system-generated emails get blocked. I wanted to do this everywhere an operation included a system-generated email to the user. I wanted to style the message in a particular way, translate it according to the user’s preferences, and I didn’t want to copy/paste it in those several places. I thought it would be difficult in case I wanted to change the styling, wording, or so on, I’d have to do it in many places. This is where an AngularJS directive becomes useful. I can define the directive in one place, and use it in many places.

And that’s it! Note that the directive in JavaScript is defined as emailSpamMessage, but in HTML as “email-spam-message”. AngularJS does the conversion for you.

Also note that in the controller associated to the HTML that the custom directive is in, needs to have the correct includes for it to work fully. For my particular example the controller will need to have $translate (angular-translate) and a CONSTANTS variable included.

ng-file-upload is a wonderful module to help you manage uploading files through AngularJS. Head on over to https://github.com/danialfarid/ng-file-upload to check it out.

One thing that isn’t obvious is how to limit the number of files that a user can upload. (This of course only applies if you are allowing multiple file uploads).

One way to limit the number of files a user can upload is through the “ngf-validate-fn” angular directive. This directive can be used to call a custom function defined in your controller that validates the file.

In this custom validation function, you can check the number of files that already exist in the files model, and return true (meaning validation passed, file should be allowed) or false (or an error name, meaning validation failed… the max number of files has reached).

Let’s say you want to limit the maximum number of files uploaded to 10. It would look like this in your html:

HOWEVER, big caveat: This will only work if the user selects one file at a time. If the user selects multiple files all at once (from the file-selection dialog box their browser presents), then this limitation trick will not work, and more files will get through. I am currently in the process of either myself implementing this feature as a native directive in the ng-file-upload module, or waiting till someone else implements it. I’ve posted this as an enhancement request on the module’s github page.

For the MEAN application I’m currently building, there is a requirement to have it served in multiple user-selectable languages. I used the MEAN fullstack generator (https://github.com/DaftMonk/generator-angular-fullstack), which does not provide i18n (internationalization) support.

When setting up my application for i18n, I realized that I needed translations available up and down the stack. So not just in the View, also in the Model and Controller. I ended up using angular-translate (https://github.com/angular-translate/angular-translate) and MomentJS (https://github.com/moment/moment/) in the client side AngularJS. And I created my own custom solution, very simple, in Node for the server side model and controller.

I think angular-translate works great in Angular, and there are plenty of guides around so I won’t go into it. But I want to mention that angular-translate doesn’t have great support (at least that I could find) for translating dates and numbers. This is where MomentJS can fill in the gaps. Again, plenty of guides out and good documentation out there for MomentJS.

For Node, I created a module that simply has a JSON of all the translations, and a function that returns the translation. Example below:

So this had me baffled for a bit. For using Angular’s $resource in your Angular service, you map it to a particular URL with (optional) parameters defined for that URL. Then how can you have multiple resources with their own unique URLs mapped in the same service?

For example, here’s a service called User which maps to the URL “/api/users/…”:

As you can see, there’s one resource in this service that maps to the one URL, so then how can I add another URL for the $resource?

The answer turned out to be pretty simple, actually. What you have to do is create an object (JSON) of $resources that are returned for the service. You can have individual elements inside the object that each map to a different $resource. So, for example:

In the above example, in the “User” service, we have two resources that can be accessed. To access “changePassword”, we can use User.WithId.changePassword (which maps to a particular URL), and to access “generateResetPasswordToken” we use User.Misc.generateResetPasswordToken (which maps to another URL).

So I’ve been working on a personal project using the MEAN stack (MongoDB, ExpressJS, AngularJS and NodeJS)! The nerd in me has been pretty excited to learn something completely new and different. I’ve never done full-stack development strictly in JavaScript, and so far I’m finding it to be pretty neat. I’ll be making posts about things I struggle with, or find useful, as I progress.

Anyway, I used the DaftMonk AngularJS full-stack yeoman generator (https://github.com/DaftMonk/generator-angular-fullstack) for my project seed. I definitely recommend it if you’re starting out fresh with MEAN (or even if you’re not), since it speeds up the initial setup and development immensely.

My problem arose as I was wiring up some post-processing to be done after a user logged in. In the login controller (login.controller.js), after the login function is called from the Auth service, there is a function in “.then()” that is called upon success.

However, even though the user has logged in, the user data is not available yet! So, you cannot access the current user’s data properties (such as their role) through Auth.getCurrentUser() (for example the Auth.getCurrentUser().role field will be undefined). This is due to the fact that the data is loaded asynchronously (I’m still trying to get the hang of how that works).

The way around this is to use the Auth.isLoggedInAsync(…callback…) function. The callback sent to isLoggedInAsync is called after the user has finally been loaded, which will guarantee your post-login-processing code being executed after the data for the user is available.